import java.util.*;
class main{
    public static void main(String args[]){
        Scanner sc=new Scanner(System.in);
        if(n==0){
                System.out.println("-1");
                return;
            }
        int n=sc.nextInt();
        if(n==0){
                System.out.println("-1");
                return;
            }
        if(n<0){
                System.out.println("Invalid Input");
                return;
            }
        int arr[]=new int[n];
        for(int i=0;i<n;i++){
            if(!sc.hasNextInt()){
                System.out.println("Invalid Input");
                return;
            }
            arr[i]=sc.nextInt();
            if(arr[i]<0||arr[i]>100){
                System.out.println("Invalid Input");
                return;
            }
        }
        int h=0;
        while(n>1){
           n=n/2;
           h++;
        }
        System.out.print(h);
    }
}